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uk.tech.digital-tv (Digital TV - General)(uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

I've noticed recently some drop outs of signal on Freeview, so I went around
the bands with my scanner and find some kind of noise that sounds a bit like
subdued arcing from about 50 Mhz all the way up to nearly 1 gig being
received on a discone just above my roof line.
Its not there all the time but for long periods.
Strangely, unlike most noises like this, it seems not to be affecting
frequencies lower than about 40 megs at all, as if its filtered.

I am at a loss to know what to do about it. of course cannot prove this is
the reason for the problems, but even the air band seems to be affected.
I've got no portable radio for this range so it will be hard to track
down. My current thinking is that its some kind of power supply for a laptop
or phone, but its none in my house!
I do think myself that somebody needs to grasp the nettle about devices
that cause radio frequency interference like power line internet adaptors
and naff switch mode power supplies for whatever device.
Eventually we could end up with a situation that nothing based on radio
reception is going to work in a built up area!
Brian

"Brian Gaff" wrote in message
...
I've noticed recently some drop outs of signal on Freeview, so I went
around the bands with my scanner and find some kind of noise that sounds a
bit like subdued arcing from about 50 Mhz all the way up to nearly 1 gig
being received on a discone just above my roof line.
Its not there all the time but for long periods.
Strangely, unlike most noises like this, it seems not to be affecting
frequencies lower than about 40 megs at all, as if its filtered.

I am at a loss to know what to do about it. of course cannot prove this is
the reason for the problems, but even the air band seems to be affected.
I've got no portable radio for this range so it will be hard to track
down. My current thinking is that its some kind of power supply for a
laptop or phone, but its none in my house!
I do think myself that somebody needs to grasp the nettle about devices
that cause radio frequency interference like power line internet adaptors
and naff switch mode power supplies for whatever device.
Eventually we could end up with a situation that nothing based on radio
reception is going to work in a built up area!

I fell foul of unknown interference on my wireless network on Monday: I'd
originally chosen Channel 1 (in the 2.4 GHz band)because none of the
channels around 1 were used by my neighbours, whereas there were weak
signals on 6 and 11. This worked fine for several years.

The other morning my wife noticed that her phone and iPad wouldn't connect
to the network. I tried all the standard things such as rebooting the router
and doing a scan with InSSIDer on my Android phone to check for interfering
networks on Channel 1 or adjacent channels. Everything looked normal:
nothing else on my channel and my SSID was visible when I scanned.

But I got authentication errors whenever I tried to connect. Everything I
tried failed - laptop, phone etc. My router also has a 5 GHz access point
and I could connect perfectly to that. But many of our devices (eg security
cameras, printer) can only talk to 2.4 GHz. Anyway, 5 GHz has a much shorter
range and is attenuated more by walls and floors.

After phoning the helpdesk for the router, we resolved it. He suggested
trying a different channel, even though InSSIDer shows no other network on
Channel 1. And as soon as I changed it to Channel 11 (which also has a very
weak signal from a neighbour's router) everything sprang into life. I wish
I'd thought to try this before phoning for help - it shows that you
shouldn't always believe scanning software!

What else uses the 2.4 GHz band, other than wireless networks? Do baby
alarms and other wireless intercoms use this band?

I've thought for a long time that there is a lot of interference coming from
my neighbour's house (joined onto our house), but so far it has only
affected the low end of the VHF/FM radio band: R2 and R4 at around 89-94 MHz
are weak and buzzy, whereas Classic FM and various local stations at around
100-104 MHz) are fine. If the guy next door wasn't a miserable,
easily-prokoved-to-anger old bugger, I'd ask him whether he's started using
any devices recently that he wasn't doing before.

Maybe whatever is causing the FM interference is now also chucking out
something on 2.4 GHz as well.

NY wrote:
as soon as I changed it to Channel 11 (which also has a very
weak signal from a neighbour's router) everything sprang into life. I wish
I'd thought to try this before phoning for help - it shows that you
shouldn't always believe scanning software!

Well the scanning software only looks for other WiFi on those channels,
the 2.4GHz band is a bit of a free-for-all, subject to power limits e.g.
bluetooth, zigbee, microwave ovens, RF parts heating, video-senders,
home cobbled-devices, etc

On 02/11/2016 10:03, Mark Carver wrote:
Are you sure it's not just 'atmospherics', there's been a lot
of activity these last few days. That's the problem now with DTT and
DAB, difficult to tell what's causing the corruption

On 02/11/2016 11:18, Andy Burns wrote:
Well the scanning software only looks for other WiFi on those channels,
the 2.4GHz band is a bit of a free-for-all, subject to power limits e.g.
bluetooth, zigbee, microwave ovens, RF parts heating, video-senders,
home cobbled-devices, etc

Yes it's a revelation when you look at the band on a general purpose
analyser.

Yes I noted this, but I'm far too close to Crystal Palace for this I think.
Certainly other signals are affected and a couple of nights back there were
lots of strange signals in foreign languages about all the way up to about
200 megs, sounded a bit like aurora stuff, but not able to prove it as have
no rotatable aerial just now. Nobody seems to make rotators with bliind
friendly tactile control boxes any more.
Brian

Funnily enough during this lift in my bedroom on just a rod without the
nasty noise present I can hear DAB from somewhere talking about Milton
Keyynes and also radio Kent. Not usually there at all.
Brian

Unfortunately my scanner stops at 2 gigs, so I don't know. Does anyone make
a conversion device to move this band down using the scanner as a tenable
IF?
That would be a handy gadget to have for checking for non digital or alien
nasties in those situations.
Brian

Of course its normally not the router signal that is the issue, its the
signal going back to the router. I don't know enough about how this works,
whether its sharing the channel or if it uses a different one according to
the one set, but I'd guess the return signal has to be weaker than the one
being put out from the router. Sadly modern ones seem not to have aerial
connectors so resiting the aerial is not so easy any more.
Simply the way a nearby mains cable runs near the routers built in aerial
is sometimes enough to stop battery powered devices connecting to it.
Brian